package queuedemo;
import java.util.LinkedList;
import java.util.Queue;


class MyStack {

    private Queue<Integer> qu1;
    private Queue<Integer> qu2;

    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }

    public void push(int x) {
        if(!qu1.isEmpty()) {
            qu1.offer(x);
        }else if(!qu2.isEmpty()) {
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
    }

    public int pop() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int size = qu1.size();
            for(int i=0;i<size-1;i++) {
                int x = qu1.poll();
                qu2.offer(x);
            }
            return qu1.poll();
        }else {
            int size = qu2.size();
            for(int i=0;i<size-1;i++) {
                int x = qu2.poll();
                qu1.offer(x);
            }
            return qu2.poll();
        }
    }

    public int top() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int size = qu1.size();
            int x = -1;
            for(int i=0;i<size;i++) {
                x = qu1.poll();
                qu2.offer(x);
            }
            return x;
        }else {
            int size = qu2.size();
            int x = -1;
            for(int i=0;i<size;i++) {
                x = qu2.poll();
                qu1.offer(x);
            }
            return x;
        }
    }

    public boolean empty() {
        return qu1.isEmpty()&&qu2.isEmpty();
    }
}
